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Anatomy Unit 2 > Ear > Flashcards

Ear Flashcards

1
Q

What is the external acoustic meatus?

A

The auditory canal, conducting sound waves from the auricle to the tympanic membrane.

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2
Q

What is the auricle?

A

A single elastic cartilage covered on both sides by hairy skin. It is continuous medially with the cartilage of the EAM.

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3
Q

What is the ear lobe and how might it be clinically important?

A

It contains no cartilage but has small blood vessels which make it a potential blood sampling site

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4
Q

What is the tragus?

A

The little flap which covers the EAM, it is just posterior to the TMJ

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5
Q

What three nerves provide sensation to the auricle?

A
  1. Great auricular (C2, C3)
  2. Lesser occipital (C2)
  3. Auriculotemporal (V3)
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6
Q

What three nerves provide sensation to the external acoustic meatus?

A
  1. V3 (auriculotemporal)
  2. CN7 (Facial nerve)
  3. CNX (vagus) -> why putting a scope in some peoples’ ears makes them cough
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7
Q

What is the cartilaginous / bony makeup of the EAM? What is in the cartilaginous part?

A

Cartilaginous - outer 1/3
Bone - Inner 2/3
All is cartilaginous for infants

Cartilaginous part has ceruminous glands which produce cerumen

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8
Q

What is the isthmus of the EAM? Clinical significane?

A

EAM narrows by about 5mm when it becomes bony - this is the isthmus
-Where foreign bodies get stuck in children

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9
Q

What is the tympanic membrane?

A

Thin, semitransparent membrane dividing the EAM from middle ear compartment. It is concave from being pulled on by the malleus, and converted sound vibrations into mechanical motion via the auditory ossicles

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10
Q

What is the innervation to the internal and external parts of the TM?

A

External: Same as EAM, essentially V3, VII, and X
Internal: CNIX (glossopharyngeal)

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11
Q

What is the umbo?

A

Central depression in the tympanic membrane formed by the malleus

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12
Q

What is the cone of light on the TM?

A

A bright area that can be seen when examining with the otoscope, points anteroinferiorly

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13
Q

What about the TM is indicative of skull fracture?

A

Severe bleeding or CSF drainage through the TM and EAM. Indicates the close proximity of external ear and middle ear divisions to the meninges of the brain

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14
Q

Where is the middle ear cavity and what are its anterior and and posterosuperior connections?

A

It is a narrow cavity in the petrous portion of the temporal bone.
Anteriorly - auditory tube
Posterosuperiology - mastoid antrum to mastoid cells

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15
Q

What is the auditory tube?

A

As opposed to the auditory canal, another name for the EAM, the auditory tube connects to the middle ear and is also called the pharyngotympanic or eustachian tube

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16
Q

What is the tegmen tympani?

A

Roof of the tympanic cavity, separates the tympanic cavity from the dura on the floor of the middle cranial fossa

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17
Q

What is related to the floor of the tympanic cavity?

A

It separates the tympanic cavity from the internal jugular vein

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18
Q

What is the lateral wall of the tympanic cavity?

A

The tympanic membrane (concave)

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19
Q

What is the medial wall of the tympanic cavity?

A

Wall separating tympanic cavity from internal ear (Concave)

20
Q

What are the structures on the medial wall of the tympanic cavity?

A
  1. Promontory of basal portion of cochlea
  2. Oval window
  3. Round window
  4. Stapes + tendon of stapes
  5. Facial nerve in facial canal
21
Q

What is the promontory of the medial wall of the tympanic cavity?

A

It is the bulge formed by the cochlea of the internal ear

22
Q

What is each window on the medial wall of the tympanic cavity?

A

Oval window - stapes is against it, it is the vestibular window which transmits the sound
Round window - cochlear window, nothing is on it and its the dampening of the sound at the end of the cochlea

23
Q

What is the facial nerve’s course in the middle ear?

A

Facial nerve enters through internal acoustic meatus in facial canal through the medial wall superiorly and enters the posterior wall to continue out between the mastoid process and the styloid process (stylomastoid foramen)

24
Q

What are the structures of the lateral wall in the middle ear?

A
  1. Malleus + incus
  2. Chorda tympani nerve
  3. Tendon of tensor tympani muscle
  4. Tympanic membrane
25
Q

Where does the chorda tympani course in the middle ear?

A
  1. Branches from the facial nerve right before stylomastoid foramen exit, courses anteriorly through the posterior wall, goes between the incus and malleus on the lateral wall, and exits anteriorly lateral to the tensor tympani tendon through the petrotympanic fissure.
26
Q

What is the tympanic nerve?

A

A branch of glossopharyngeal nerve (CNIX), courses through hole in floor of tympanic cavity and spreads out across the round promontory as the tympanic plexus

27
Q

What is the function of the tympanic plexus?

A

Formed on the promontory by the tympanic nerve (CN9), it supplies sensory innervation to middle ear mucosa. It also has axons that exit the middle ear cavity as the lesser petrosal nerve to provide preganglionic PANS to the otic ganglion (to parotid)

28
Q

What are the two major structures on the posterior (mastoid) wall of the middle ear cavity?

A
  1. Mastoid antrum - entrance to mastoid air cells, located superiorly
  2. Pyramidal project of bone which contains the stapedius muscle
29
Q

What are the two major structures in the anterior (carotid) wall of the middle ear cavity?

A

Two openings:

  1. Superior - transmits tensor tympani muscle, whose tendon will attach to the malleus
  2. Inferior - opening to auditory tube
30
Q

What is the structure of the auditory tube?

A

Funnel-shaped with wide end towards the nasopharynx. 1/3 closest to anterior wall of middle ear cavity is bony, 2/3 is cartilaginous. It is lined with mucous membrane that is continuous with middle ear and nasopharynx

31
Q

What is the function of the auditory tube?

A

To equalize pressure of the middle ear cavity with atmospheric pressure. It is closed except during swallowing or yawning when tensor veli palatini and salpingopharyngeus muscles contractions open the tube.

32
Q

Why does infection of the adenoids pose a problem for the middle ear cavity?

A

If it spreads to the tubal tonsils, ultimately mild infections can cause mucous membranes of auditory tube to swell, closing it off and reducing pressure in middle ear cavity. This prevents the free movement of the tympanic membrane and can diminish hearing.

33
Q

What is the significance of the mastoid air cells?

A

Infections of these cells can be transmitted through the mastoid antrum during otitis media. They can usually be treated by antibiotics

34
Q

When would you do a mastoidectomy and what is the risk?

A

For persistent mastoid infections that are not treatable by antibiotics, you can remove the mastoid through the posterior wall of the EAM.

Risk - damage of CN7 in facial canal prior to exiting the stylomastoid foramen

35
Q

What bones are involved in the conduction of sound to the oval (vestibular) window? How does this work?

A

Malleus, incus, and stapes.
Handle of malleus is embedded into the tympanic membrane. Head of malleus moves which is in contact with the incus. Incus contacts stapes with its base in oval window

36
Q

What is the attenuation reflex?

A

Reflex to reduce the intensity of sound waves to inner ear, preventing damage. Carried out by tensor tympani and stapedius.

37
Q

What is the tensor tympani?

A

Muscle whose tendon comes from the anterior wall of the middle ear cavity and inserts on the malleus, it tenses the tympanic membrane and dampens vibrations.
-Innervated by CN V3!

38
Q

What is the stapedius?

A

Muscle inserting onto stapes, prevents excessive movement at the oval window.
-Innervated by CN VII (branch from facial canal before it exits stylomastoid foramen})

39
Q

What causes hyperacusia?

A

Paralysis of either stapedius or tensor tympani, most commonly stapedius (as in Bell’s palsy). Causes sounds to be excessively loud

40
Q

Why does the attenuation reflex not help for explosions?

A

When it is too sudden, the muscles cannot dampen the sound

41
Q

What frequency is the attenuation reflex best for and why?

A

It is best at attenuating low frequency sounds, so that we can hear high-frequency sounds easier whenever there are lots of low frequency sounds around.
-Good because people’s voices are high frequency.

42
Q

What is otosclerosis?

A

Bony overgrowth around the stapes and oval window that stops the movement of auditory ossicles and diminishes hearing

43
Q

Where is CN8 embedded?

A

The vestibular and cochlear divisions are embedded in the petrous portion of the temporal bone, and enter through the internal acoustic meatus

44
Q

What is the bony labyrinth? What fluid fills it?

A

Bone cavities of internal area, which includes the vestibule, 3 semicircular canals, and the cochlea. They are all lined with periosteum and filled with perilymph

45
Q

What is the membranous labyrinth? What fluid fills it?

A

Membranous ducts and sacs that consist of the semicircular ducts, cochlear ducts, utricle & saccule (for linear accelerations)

Filled with endolymph

46
Q

What is the vestibular apparatus?

A

The organ of balance, consisting of the semicircular canals, utricle, and saccule. They detect linear and angular acceleration of the head.

47
Q

What is the cochlea? What is the sound amplification?

A

The organ of hearing, detects movement of auditory ossicles against the oval window. The ear ossicles amplify sounds 20x to improve definition. (Loud sounds must be dampened)

Anatomy Unit 2 (13 decks)

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